Minor Updates: Fixes for #521 and #699

[unoebauer]

A small PR which fixes

• tardis/data/tardis_example_config.yml is not a valid config file #521 by removing the deprecated example config in the Tardis data directory; a recent, working version of the example config will be maintained on https://github.com/tardis-sn/tardis-refdata
• [OpenMP] Use OMP_NUM_THREADS by default #699 by changing the default nthreads value in the schema from 1 to 0 (and adding a comment about the 0 behaviour)

[wkerzendorf]

I guess we hope no one needs the example config in data